A digital signature is a mechanism that is used to verify that a particular digital document, message or transaction is authentic.

Non-repudiation: Repudiation refers to any act of relinquishing responsibility for a message. Non-repudiation ensures that the signer who digitally signed the document cannot deny having signed it. The digitally signed documents strengthen its recipient integrity claims. Therefore, the recipient can strongly insist on the signature of the sender so as not to be easily denied at a later time.

Information leakage: The leakage of trade secrets in E-commerce mainly includes two aspects: (a) the content of the transaction between the vendor and customer is stolen by the third party; (b) the documents provided by the merchant to the customer or vice versa are illegally used by the another. This intercepting and stealing of Online documents is called information leakage.

"3-D Secure is a secure payment protocol on the Internet. It was developed by Visa to increase the level of transaction security, and it has been adapted by Master Card. It gives a better authentication of the holder of the payment card, during purchases made on websites. The basic concept of this (XML-based) protocol is to link the financial authorization process with an online authentication system. This authentication model comprise 3 domains (hence the name 3D) which are:
1. The Acquirer Domain
2. The Issuer Domain
3. The interoperability Domain

(i) The certificate authority maintains a database of public keys called repository so that it can verify the user with digital signatures.
(ii) Expired certificates are usually deleted from the database by the certificate authority.

1. The most common cryptographic protocol is Secure Sockets Layers (SSL). SSL is a hybrid encryption protocol for securing transactions over the internet. The SSL standard was developed by Netscape in collaboration with Mastercard, Bank of America, MCI and silicon graphics.
2. Today, all browsers in the market support SSL, and most of the secure communication are proceeded through this protocol. SSL works completely hidden for the users, who does not have to intervene in the protocol.
3. The only thing the user has to do is make sure on URL starts with https://instead of http:// where "s" obviously means secured.
4. SSL was renamed as TLS (Transport Layer Security) in 2001.

As the security issue is the most worrying issue for E-Business, ensuring the security of E-Commerce activities has become the core research field of E-Commerce. The following are some of the security elements involved in E-Commerce.
(i)  Authenticity:( conforming genuineness of data shared.
(ii) Availability:prevention against data delay or removal.
(iii) Completeness: unification of all business information.
(iv) Confidentiality: protecting data against unauthorized disclosure.
(v) Effectiveness: effective handling of hardware, software and data.
(vi) Integrity: prevention of the data being unaltered.
(vii) Non-repudiation: prevention against violation agreement after the deal.
(viii) Privacy:prevention of customers personal data being used by others.
(ix) Reliability: providing a reliable identification of the individuals or businesses.
(x) Review ability: capability of monitoring activities to audit and track the operations.